package LC;

/**
 * https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/
 * Given a linked list,
 * remove the nth node from the end of list and return its head.
 * For example,
 * Given linked list: 1->2->3->4->5, and n = 2.
 * After removing the second node from the end,
 * the linked list becomes 1->2->3->5.
 */
public class LC_019_RemoveNthNodeFromEndofList_LinkedList {
    public static void main(String[] args) {
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        head.next.next = new ListNode(3);
        head.next.next.next = new ListNode(4);
        head.next.next.next.next = new ListNode(5);
        ListNode listNode = removeNthFromEnd(head, 2);
        while (listNode != null) {
            System.out.print(listNode.val + " ");
            listNode = listNode.next;
        }
    }

    static class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    private static ListNode removeNthFromEnd(ListNode head, int n) {
        if (head == null || n < 1) return head;

        ListNode cur = head;
        while (cur != null) {
            n--;
            cur = cur.next;
        }

        if (n == 0) head = head.next;

        if (n < 0) {
            cur = head;
            while (++n != 0) cur = cur.next;
            cur.next = cur.next.next;
        }
        return head;
    }
}
